Old users can't log in using IE but new users can

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I have a fresh install of 5.6.2.1 with no issues

but I have 2 sites that have been slowly updated though the years that users can not log into using IE. I have edited all the security settings and tried changing the site.php and checking php(all the different reason people seem to have on the forms)but I come up empty

now the strange

Older accounts do not work with IE.. However if I register a new account that account will work with IE.

I'm lost and confused

SheldonB